Compositions and methods for the introduction of elastomeric reinforcement fibers in asphalt cement concrete

ABSTRACT

The present invention relates to elastomeric polymer fiber reinforced asphalt cement concrete for use in a variety of applications. In particular, the reinforcement fibers are effective to reduce or preclude voids and/or cracks formed in the asphalt upon placement and to render a self-healing property to the placed asphalt.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/519,096 filed Jul. 23, 2019, entitled “Compositions and Methods forthe Introduction of Elastomeric Reinforcement Fibers in Asphalt CementConcrete”, that issues as U.S. Pat. No. 10,927,257 on Feb. 23, 2021,which is a continuation of and claims priority to U.S. patentapplication Ser. No. 15/049,476 filed Feb. 22, 2016, entitled“Compositions and Methods for the Introduction of ElastomericReinforcement Fibers in Asphalt Cement Concrete”, that issued as U.S.Pat. No. 10,392,508 on Aug. 27, 2019, which claims priority under 35U.S.C. § 119(e) to U.S. Provisional Patent Application Ser. No.62/118,677, filed Feb. 20, 2015, entitled “Compositions and Methods forthe Introduction of Elastomeric Reinforcement Fibers in Asphalt CementConcrete”, which are herein incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to reinforcement fibers and methods ofintroducing and distributing reinforcement fibers into asphalt cementconcrete, and, more particularly, to reinforcement fibers composed ofelastomeric material, which provide a self-healing property to fieldplaced asphalt cement concrete.

BACKGROUND OF THE INVENTION

Various reinforcement fibers and their use in a wide variety ofapplications are known in the art. For example, it is known to addreinforcement fibers to building materials, such as, asphalt cementconcrete and the like, to add strength, toughness, and durability, andto improve the integrity of the asphalt properties. In someapplications, reinforcement fibers are added to asphalt to reduce orprevent cracks. Typical reinforcement fibers include asbestos fibers,glass fibers, steel fibers, mineral fibers, natural fibers, syntheticfibers, such as polymer and aramid fibers, and cellulose fibers. Somereinforcement fibers are better suited for particular applications thanothers. For example, asbestos fibers are known to provide effectivereinforcement but, due to environmental and health concerns, thesefibers are not extensively used. In addition, some fibers are relativelyexpensive and therefore, not practical for all applications.

Reinforcement fibers are incorporated into the building materials, suchas, asphalt cement concrete, using a variety of conventional methods andtechniques. For example, it is known to add reinforcement fibers to anasphalt cement concrete composition during the manufacturing processprior to field placement. For example, in a batch process wherein amixing machine is used to produce asphalt, reinforcement fibers areadded to a mixing chamber having mixing blades, with other ingredients.In a continuous process that uses a drum mixer, the reinforcement fibersare added to the drum mixer. The reinforcement fibers may be added toequipment other than the mixing chamber and the drum mixer. In general,the reinforcement fibers may be added to any associated machinerypositioned either before or after the mixing machine or the drum mixerprovided that the machinery has the capability to provide sufficientmixing and dispersion of the reinforcement fibers in the asphaltcomposition. In some instances, the reinforcement fibers are added priorto introducing the liquid asphalt. In other instances, such as, formicro-surfacing and slurry seal, the reinforcement fibers are addedsimultaneously with other ingredients in the asphalt mixture.

The reinforcement fibers are added to a cement concrete compositioneither individually or in a bundle or in a container, e.g., bag, coatingor the like. Generally, it is advantageous for the reinforcement fibersto be added in a manner that is effective to reduce or minimizeentanglement and clumping, and to improve or maximize distributionthroughout the composition.

Further, reinforcement fibers can be added to an asphalt cement concretecomposition in varying amounts. Typically, the amount added is such thatdesired properties of the reinforced asphalt are achieved upon fieldplacement.

There is a continuous desire and need in the art to improve the abilityof reinforcement fibers to disperse uniformly within an asphalt cementconcrete composition, as well, as the ability to provide improvedstrength, toughness and durability to cement concrete when it is fieldplaced. For example, there is a desire to provide reinforcement fibersthat have elastic or stretchable properties that are capable to improvethe strength, toughness and durability, and essentially to provide aself-healing property, to field placed asphalt cement concrete.

It is recognized in the asphalt cement concrete industry that there arecracking problems associated with micro-surfacing (MS), which consistsof applying a layer of new pavement over existing pavement. Cracking inthe MS layer can occur within only months following its placement. Thereis a need for a more flexible, non-cracking MS treatment, however, thereis also a concern that if the MS is too soft, it will rut. Thus, theelastomeric polymer reinforcing fibers of the invention are capable ofretarding crack propagation and promoting self-healing to extendpavement life in conventional MS or can be designed with softer binderto reduce rut potential. Reducing cracks in the MS layer can preventwater intrusion, which is known to cause significant damage to highways.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides a reinforcementcomposition including a plurality of reinforcement fibers composed of anelastomer, e.g., elastomeric polymer. The elastomeric polymer can beselected from a wide variety of elastomers known in the art and, ingeneral, includes a material that is capable of deforming e.g.,stretching or elongating, when a force is applied to the material andthen, substantially resuming, e.g., reverting back, to its originalshape or configuration when the force is removed. The elastomericpolymer can include material having an aspect ratio from about 20 toabout 5,000. Further, the plurality of reinforcement fibers can eachhave a denier from about 20 to about 1500 and a length from about1/16-inch to about 3 inches. In certain embodiments, the reinforcementfibers are composed of synthetic polymer including polyurethane, suchas, spandex. Further, the elastomeric polymer can include naturalpolyisoprene and synthetic polyisoprene. The elastomeric polymer can beselected from polybutadiene, chloroprene rubber, polychloroprene rubber,butyl rubber, styrene-butadiene rubber, nitrile rubber and mixturesthereof. In certain embodiments, the elastomeric polymer can be selectedfrom ethylene propylene rubber, ethylene propylene diene rubber,epichlorohydrin rubber, polyacrylic rubber, silicone rubber,fluorosilicon rubber, fluoroelastomers, perfluoroelastomers, polyetherblock amides, chlorosulfonated polyethylene, ethylene-vinyl acetate andmixtures thereof.

The elastomeric polymer can be scrap, trim or other material that, ifnot used in the invention, would be considered waste and disposed ofappropriately, such as, but not limited to, disposal in a landfill. Thisform of the elastomeric polymer is referred to herein as recycledmaterial.

In certain embodiments, the reinforcement composition can furtherinclude a plurality of non-elastomeric reinforcement fibers, which aremixed or blended with the plurality of elastomeric polymer reinforcementfibers. The non-elastomeric reinforcement fibers may be composed ofpolymer, such as, but not limited to, polyolefin, aramid, polyester,nylon and mixtures thereof. Polyolefin can include, but is not limitedto, polyethylene, polypropylene and mixtures thereof.

The plurality of reinforcement fibers can be in a form selected fromindividual fibers, a bundle of fibers, a container of fibers andcombinations thereof. The container can be in the form of a wrap, layer,film, coating or bag. The container may be constructed of a materialthat at least partially melts, dissolves, disintegrates or breaks apartto release the reinforcement fibers into an asphalt cement concretecomposition. In certain embodiments, the container can be composed ofpolyolefin, such as polypropylene, polyethylene and mixtures thereof.

The plurality of elastomeric polymeric fibers can serve as acarrier/buffer material for the plurality of non-elastomeric fibers.

The plurality of reinforcement fibers is introduced and distributed intoasphalt cement concrete prior to its field placement. Upon placement andthereafter, the elastomeric reinforcement fibers promote or provide aself-healing property to the placed asphalt. Thus, in another aspect,the present invention provides a self-healing asphalt that includes aplurality of reinforcement fibers including elastomeric polymer, andaggregate.

In still another aspect, the present invention provides a method ofproducing reinforced asphalt cement concrete. The method includesproviding aggregate, providing a plurality of reinforcement fibersincluding elastomeric polymer and, introducing and distributing thereinforcement fibers into the aggregate to produce reinforced asphaltcement concrete.

The elastomeric polymer reinforcement fibers can be added at varioussteps during the manufacture process and further, can be added prioradding liquid asphalt or coincident with all ingredients of the asphaltmix.

DETAILED DESCRIPTION OF THE INVENTION

The present invention broadly relates to asphalt cement concrete,reinforcement fibers, methods of making fiber-reinforced asphalt cementconcrete compositions, and methods of using the compositions for fieldplacement applications. At least a portion of the reinforcement fibersadded to the asphalt cement concrete compositions includes elastomericpolymer.

As used herein and the claims, the term “fiber(s)” is meant to includematerials and forms that are traditionally understood by one of ordinaryskill in the art to constitute a fiber as well as materials having anaspect ratio from about 20 to about 5,000. The fiber(s) in accordancewith the invention have a denier from about 20 to about 1500 and alength from about 1/16-inch to about 3 inches.

As used herein and the claims, the terms “cement concrete” and “asphalt”mean asphalt cement concrete. The term “asphalt cement concrete” refersto the use of asphalt cement. The term “cement” refers to the binderthat holds together the concrete. As used herein, the cement also can bereferred to as “binder” or “liquid asphalt.” The term “concrete” refersto a gradation of fine and coarse aggregate, such as, but not limited tosand and rock.

As used herein, the term “elastomeric polymer” and related terms, suchas, “elastomer”, “elastic polymer” and the like, generally refer to anymaterial that is able to substantially resume its original shape when adeforming force is removed. When force is applied to an elastomer,molecules straighten out in the direction in which they are pulled andupon release, the molecules spontaneously return to their normalcompact, random arrangement. This property is often referred to aselastic or stretchable.

It is known in the art that an elastomer is a polymer withviscoelasticity, e.g., having both viscosity and elasticity, as well as,very weak inter-molecular forces, low Young's modulus and high failurestrain as compared with other materials. Elastomeric polymers caninclude polyurethanes, polyesters and, co-polymers and mixtures thereof.In certain embodiments, suitable reinforcement fibers for use in theinvention include fibers composed of synthetic polymer, e.g., long-chainsynthetic polymer, which includes polyurethane, such as but not limitedto, at least about 85% polyurethane. For example, a synthetic fiber thatis made up of long chain polyurethane-containing polymer is known in theart as spandex or elastane, and may be commercially available under thetrade name LYCRA®. In general, the synthetic polyurethane-containingpolymer, e.g., spandex, can be prepared by reacting monomer, such as butnot limited to, polyester, with diisocyante to form a pre-polymer. Thepre-polymer undergoes chain extension, such as, by reaction withdiamine, is cured and then drawn out to produce the resulting fibers.

The term “elastomer” is often used interchangeably in the art with theterm “rubber”, including natural and synthetic rubber. Elastomers areusually thermoset materials, which require curing, e.g., vulcanization,but may also be thermoplastic. Long polymer chains cross-link duringcuring, e.g., vulcanizing. The elasticity is derived from the ability ofthe long chains to reconfigure themselves to distribute an appliedstress. Covalent cross-linkages ensure that the elastomer will return toits original configuration when the stress is removed. As a result ofthis flexibility, elastomers can reversibly extend from about 5 to about700%, depending on the specific material composition. At ambienttemperatures, elastomers are relatively soft and deformable. Each of themonomers which link to form the polymer is usually made of carbon,hydrogen, oxygen and/or silicon.

In addition to the polyurethane-containing synthetic polymer fibers,e.g., spandex fibers, the present invention includes fibers composed ofother elastomers, e.g., rubbers. Non-limiting examples includeunsaturated rubber that can be cured by sulfur or non-sulfurvulcanization, such as, but not limited to, natural polyisoprene, e.g.,cis-1,4-polyisoprene natural rubber and trans-1,4-polyisoprenegutta-percha, synthetic polyisoprene, polybutadiene, chloroprene rubber,polychloroprene rubber, butyl rubber, e.g., copolymer of isobutylene andisoprene, styrene-butadiene rubber, e.g., copolymer of styrene andbutadiene, nitrile rubber, e.g., copolymer of butadiene andacrylonitrile, and mixtures thereof.

Further, non-limiting examples of elastomers for the reinforcementfibers include saturated rubbers that cannot be cured by sulfurvulcanization, such as, but not limited to, ethylene propylene rubber,e.g., copolymer of ethylene and propylene, ethylene propylene dienerubber, e.g., terpolymer of ethylene, propylene and diene-component,epichlorohydrin rubber, polyacrylic rubber, silicone rubber,fluorosilicon rubber, fluoroelastomers, perfluoroelastomers, polyetherblock amides, chlorosulfonated polyethylene, ethylene-vinyl acetate, andmixtures thereof.

Other non-limiting examples of elastomers include thermoplasticelastomers and polysulfide rubber.

It is contemplated that the elastomeric polymer can be a recycledmaterial. As used herein and the claims, the terms “recycled”, “recycle”and the like, refer to elastomeric polymer material that is scrap, trimor waste. That is, if the material was not employed in the invention toproduce reinforcement fibers, the material would be considered unusableand would be disposed of appropriately, such as , but not limited to,being disposed of in a landfill.

The plurality of reinforcement fibers can include varying lengths. Forexample, as mentioned herein, each of the reinforcement fibers can havea length in the range from about 1/16-inch to about 3 inches. Withoutintending to be bound by any particular theory, it is believed thatusing fibers of different lengths allows for variable strain ranges incement concrete that is placed and set. For example, shorter lengthsassist in reinforcing or holding together smaller strain areas, whilelonger length fibers assist in bridging higher strain or movement in thecement concrete. Further, the plurality of reinforcement fibers can becomposed of a recycled material that is re-purposed for use in cementconcrete or manufactured as a new material specifically for use asreinforcement fibers in cement concrete.

In general, the elastomeric polymer fibers provide improved stability,durability and flexibility to asphalt cement concrete. For example, theelastomeric polymer fiber-reinforced asphalt cement concretecompositions of the present invention exhibit at least one of thefollowing benefits as compared to conventional asphalt concretes: (i)reduces cracking, rutting, raveling, pot holes and other distresses inplaced asphalt; (ii) reduces mix segregation; (iii) promotesself-healing; (iv) reduces drain down in Stone Matrix Asphalt, PorousFriction Courses, and open Graded Friction Courses mixes; (v) increasesinsulation value to reduce frost depth under placed cement concrete;(vi) assists in distribution of other different fibers; and (vii)results in quieter placed cement concrete.

As used herein, “self-healing” refers to the following phenomena: placedasphalt cement concrete contracts during cold weather and as a result,cracks are formed and, the elastomeric polymer reinforcement fibers areloaded in tension and remain in tension until warmer weather to assistin pulling the pavement back together. Therefore, promoting self-healingof the cracks.

In addition to the elastomeric polymer reinforcement fibers, thecomposition of the invention can also include non-elastomericreinforcement fibers, e.g., a blend of elastomeric and non-elastomericfibers. The non-elastomeric reinforcement fibers may be selected from awide variety of reinforcement fibers known in the art, includingsynthetic fibers, such as, polymer fibers, e.g., polyolefin fibers,e.g., polyethylene and/or polypropylene fibers, polyester fibers, aramidfibers, polyamide fibers, polyvinyl-chloride fibers, nylon fibers andnatural fibers, and mixtures thereof.

In general, reinforcement fibers can be used in various shapes, sizes,and forms. The reinforcement fibers, for example, can be flat, such asin the form of a sheet, or cylindrical, such as in the form of a tube orcord. The reinforcement fibers may include a deformation, such as a oneor more crimps, in the flat or cylindrical length of the fiber. Thedeformation, e.g., crimp(s), can form a fiber having different shapessuch as z-shaped, s-shaped, w-shaped and wedge-shaped fibers. In certainembodiments, loose fibers can be difficult to handle, and therefore, itmay be desirable to configure and control the fibers, such as to improvethe ease of handling, e.g., for adding the fibers to an asphalt mix.Accordingly, the sheets, tubes or cords can be bundled together in acontainer. The term “container” is used broadly to include a means ofholding together the reinforcement fibers and, as such, can include acircumferential wrap or layer/film or a coating or a bag. The containercan be composed of cellulose or polyolefin, such as polyethylene,polypropylene and mixtures thereof. The composition of the container canfurther include other additives, such as those typically used inpreparing asphalt.

The fibers, individually or together in various combinations andproportions, can be fibrillated (i.e., pulled apart to form a net likestructure) or non-fibrillated. The fibers can be configured in apredetermined number of twists and turns.

In the present invention, the denier of the reinforcement fibers canvary. For example, as mentioned herein, each of the reinforcement fiberscan have a denier in the range from about 20 to about 1500. The deniercan depend on the material composition of the reinforcement fibers,their configuration (e.g., monofilament, bundled, fibrillated,non-fibrillated, twisted, and turned), and their intended use orapplication.

The fibers may be cut to a predetermined length using conventionaltechniques and methods known for cutting fibers. In general, it isbelieved that longer fibers are capable of improved bonding in theasphalt cement concrete.

In accordance with certain embodiments of the invention, thereinforcement fibers are introduced, e.g., admixed, into an asphaltcomposition, e.g., mix, prior to field placement using various knownmethods, techniques and apparatus. The fibers can be introduced into theasphalt mix during one or more of various steps or locations in themanufacture process. For example, the reinforcement fibers can be addedto a mixing machine or associated machinery, in a hopper, or in atransportation vehicle. In general, the reinforcement fibers can beadded at any step or location in the process prior to field placement ofthe asphalt provided there is sufficient mixing that occurs in the stepor at the location to adequately incorporate the reinforcement fibersinto the asphalt mix.

As mentioned, the reinforcement fibers can be added as individual fibersor in bundles and containers to the asphalt mix during the manufacturingprocess. When added in containers, each container can hold elastomericand non-elastomeric reinforcement fibers or each container can holdeither elastomeric fibers or non-elastomeric fibers. The container canbe operable to hold the reinforcement fibers and then to release them asneeded. Thus, the container can be composed of a material that iscapable of at least partially melting, dissolving, or disintegrating,e.g., breaking apart, to release the reinforcement fibers when combinedand mixed with the asphalt mix. In certain embodiments, the containermay be constructed of a material such that when subjected to mixingand/or agitation, e.g., mixing blades of the mixing machine, thecontainer at least partially breaks apart and is dispersed within themix. In another embodiment, the container may be constructed of amaterial such that when subjected to heating, which reaches or exceedsits transition or melting temperature, the container at least partiallymelts and/or dissolves, and is dispersed within the asphalt mix.

In certain embodiments, air or pneumatics, e.g., an air or a pneumatictransport device, may be used to introduce and distribute thereinforcement fibers into the asphalt mix. In these embodiments, thereinforcement fibers can be essentially blown into the asphalt mix.Suitable transport devices are known in the art and can be employedas-is or can be adapted for particular conditions. Without intending tobe bound by any particular theory, it is believed that employing themechanism of air or pneumatics (as compared to, for example, manualaddition) to incorporate the reinforcement fibers into the asphalt mixprovides improved distribution and dispersion of the reinforcementfibers. Typically, the transport device is part of, e.g., an integralpart of, or is connected to one or more parts (e.g., apparatus, pipingor the like) of the asphalt manufacturing equipment. Further, thetransport device typically includes an input reservoir or pipe toreceive the reinforcement fibers and an output tube or pipe to dischargeand feed the reinforcement fibers into the asphalt mix.

In accordance with the present invention, the use of elastomeric polymerreinforcement fibers can result in at least one of improved strength,durability, toughness, integrity, and self-healing upon field placementof the resulting reinforced asphalt, as compared to a reinforced asphaltproduced by employing reinforcement fibers which do not includeelastomer.

In addition to the reinforcement fibers, the compounds used in producingasphalt include, but are not limited to, aggregate and binder, e.g.,liquid asphalt.

The manufacture of asphalt cement concrete consists of employing athermal process and therefore, includes heating the ingredient, e.g.,aggregate and liquid asphalt, in the chamber of an asphalt mixingmachine. The temperature of the asphalt cement concrete composition canvary and can include those temperatures typically used incommercially-operated asphalt manufacturing facilities. In an embodimentof the present invention, the temperature can be within a range of aboutambient temperature to about 375° F.

The reinforcement fibers can be added to the asphalt mix in varyingamounts. Typically, the amount added is such that desired properties ofthe asphalt are achieved. In certain embodiments, the reinforcementfibers can be at most 5.0 percent or greater by volume per ton of theasphalt mix. In yet another embodiment of the invention, thereinforcement fibers can be in a range from about 0.0065 percent toabout 5.0 percent by volume per ton of the asphalt mix. In certainembodiments, a one pound package, metered and dosed, of thereinforcement fibers is added to the asphalt mix.

The reinforced asphalt cement concrete of the invention can be used in awide variety of applications, for example, in structural pavements,airport runways and tarmacs, bridge deck overlays, floors, and likeasphalt products. The reinforced asphalt of the invention may also beused for repair, rehabilitation, retrofit, and renovation of existingproducts or structures, such as, for example, in overlays,micro-surfacing and repairs of airport pavements, bridge decks, parkingareas, roadways, and the like, including patching and filling potholes.

In addition to reinforcement, incorporation of the elastomeric polymerreinforcement fibers of the present invention in asphalt modifies thecracking mechanism and reduces the propagation of micro-cracking causedby a number of factors. It is believed that relative to non-reinforcedasphalt, the resultant cracks of fiber reinforced asphalt of the presentinvention are smaller in width, the permeability of the material isreduced, and the ultimate cracking strain is enhanced. Furthermore, theelastomeric polymer fibers employed in the present invention are capableof carrying a load across the crack. As a result, the asphalt may haveat least one change in its material properties, such as toughness,residual load carrying ability after the first crack, and impactresistance. Moreover, it is believed that the elastomeric polymerreinforcement fibers used in the present invention produce an asphalthaving improved strength compared to non-reinforced cement concrete orcement concrete reinforced in the absence of elastomeric polymerreinforcement fibers, such that the asphalt of the present invention canbe suitable for locations where the asphalt will experience both highand low temperatures and areas subjected to heavy loadings (e.g., hightraffic areas) and heavy concentrations of truck traffic as well as manyother uses.

One example of reinforcement fibers in accordance with the inventioninclude elastomeric polymer reinforcement fibers known under the tradename FORTA FLEX, which are available from Forta Corporation in GroveCity, Pa.

The elastomeric polymer fibers suitable for use in the present inventionare different and distinguishable from known reinforced cement concretethat includes ground rubber tires. It is known in the art to grindrubber tires, i.e., used or worn out, and use the ground rubber tireaggregate or particulate in cement concrete compositions. This materialdoes not exhibit the elastomeric properties nor the fiber form nor theaspect ratio associated with the reinforcement fibers of the inventionand therefore, ground rubber tires, and rubber aggregate or rubberparticulates produced therefrom, are not considered suitable for use inthe invention.

EXAMPLES

The performance of elastomeric polymer reinforcement fibers in placedconcrete under cold weather conditions was simulated as follows.Elastomeric polymer (spandex) fibers were purchased as scrap materialhaving varying denier and cut into varying lengths. There was added 3grams of the elastomeric polymer reinforcement fibers to a 4-inchdiameter container having a 1-inch depth. The container was filled withwater and then set in a freezer until frozen solid. A control sample wasmade using the same process with the exception that the control sampledid not include any of the reinforcement fibers.

After freezing was complete, the control sample was dropped from aheight of 4 feet onto a concrete floor. The control sample shatteredinto many pieces. The elastomeric polymer fiber-reinforced sample wasdropped three times from the same height. Micro-cracking in the specimenwas visually observed but no pieces broke off, and the original shape ofthe sample was maintained. The fiber sample was then forcibly throwndown onto the concrete floor in an effort to break the sample. Onlysmall pieces or chips broke off around the edges of the sample. Thesmall pieces or chips were essentially equivalent in size to ice chipsin a snow cone. The sample was then thrown over hand, like a baseball,at concrete steps. As a result, the sample maintained its shape with nochunks or pieces breaking off, and it rolled down the steps.

In a trial project, about 30 pounds of elastomeric polymer fiber(spandex)-reinforced cement concrete was placed to form new pavementover existing pavement. The approximate length of the test section was150 feet at a ⅝-inch depth. The reinforcement fibers mixed well in themicro-surfacing material and no problems were encountered. It wasvisually observed that the fibers bonded well with the asphalt emulsion.The fibers took on the color of the asphalt. Field observations showedthat in some places the fibers aligned in the direction of paving. Fiberalignment contributes to good quality specifically for retardingTransverse Reflective Cracking (TRC), which is caused by existing cracks(perpendicular to the direction of travel, usually caused by existingold concrete slab pavement), in the pavement layers below the surface ofnew pavement. These existing cracks can then migrate through the newpavement layer. The reinforcement fibers when placed in the new layerwill be positioned perpendicular to the potential area of TRC helping toprevent and retard cracking, and heal the pavement.

While specific embodiments of the invention have been described indetail, it will be appreciated by those skilled in the art that variousmodifications and alternatives to those details could be developed inlight of the overall teachings of the disclosure. Accordingly, theparticular arrangements disclosed are meant to be illustrative only andnot limiting as to the scope of the invention which is to be given thefull breadth of the claims appended and any and all equivalents thereof.

What is claimed is:
 1. A fiber-reinforced asphalt composition,comprising: asphalt; and a plurality of reinforcement fibers composed ofelastomeric polymer, and absent of material selected from the groupconsisting of ground rubber tire, tire aggregate and tire particulate,wherein the elastomeric polymer is selected from the group consisting ofnatural polyisoprene and synthetic polyisoprene.
 2. The asphaltcomposition of claim 1, wherein the plurality of reinforcement fibershas an aspect ratio from about 20 to about 5000, a denier from about 20to about 1500, and a length from about 1/16-inch to about 3 inches. 3.The asphalt composition of claim 1, wherein the reinforcement fibers arein the form of individual fibers, one or more bundles, one or morecontainers and combinations thereof.
 4. The asphalt composition of claim1, wherein the fiber-reinforced asphalt composition further comprisesnon-elastomeric reinforcement fibers.
 5. The asphalt composition ofclaim 4, wherein the non-elastomeric reinforcement fibers are selectedfrom the group consisting of polyolefin fibers, aramid fibers, andmixtures thereof.
 6. The asphalt composition of claim 4, wherein theplurality of reinforcement fibers composed of elastomeric polymer serveas a carrier for the non-elastomeric reinforcement fibers.
 7. Afiber-reinforced asphalt composition, comprising: asphalt; and aplurality of reinforcement fibers composed of elastomeric polymer, andabsent of material selected from the group consisting of ground rubbertire, tire aggregate and tire particulate, wherein the elastomericpolymer is selected from the group consisting of polybutadiene,chloroprene rubber, polychloroprene rubber, butyl rubber,styrene-butadiene rubber, nitrile rubber and mixtures thereof.
 8. Theasphalt composition of claim 7, wherein the fiber-reinforced asphaltcomposition further comprises non-elastomeric reinforcement fibers. 9.The asphalt composition of claim 7, wherein the non-elastomericreinforcement fibers are selected from the group consisting ofpolyolefin fibers, aramid fibers, and mixtures thereof.
 10. Afiber-reinforced asphalt composition, comprising: asphalt; and aplurality of reinforcement fibers composed of elastomeric polymer, andabsent of material selected from the group consisting of ground rubbertire, tire aggregate and tire particulate, wherein the elastomericpolymer is selected from the group consisting of ethylene propylenerubber, ethylene propylene diene rubber, epichlorohydrin rubber,polyacrylic rubber, silicone rubber, fluorosilicon rubber,fluoroelastomers, perfluoroelastomers, polyether block amides,chlorosulfonated polyethylene, ethylene-vinyl acetate and mixturesthereof.
 11. The asphalt composition of claim 10, wherein thefiber-reinforced asphalt composition further comprises non-elastomericreinforcement fibers.
 12. The asphalt composition of claim 10, whereinthe non-elastomeric reinforcement fibers are selected from the groupconsisting of polyolefin fibers, aramid fibers, and mixtures thereof.13. A fiber-reinforced asphalt, comprising: asphalt cement; a pluralityof reinforcement fibers composed of elastomeric polymer, and absent ofmaterial selected from the group consisting of ground rubber tire, tireaggregate and tire particulate; and aggregate, wherein the plurality ofreinforcement fibers promotes healing of cracks formed withinfield-placed fiber-reinforced asphalt, and wherein the elastomericpolymer is selected from the group consisting of natural polyisopreneand synthetic polyisoprene.
 14. The asphalt of claim 13, wherein saidreinforcement fibers have an ability in the field-placedfiber-reinforced asphalt to stretch beyond their original shape and thento subsequently resume their original shape to heal cracks.
 15. A methodof preparing fiber-reinforced asphalt, comprising: providing asphalt;providing aggregate; providing a plurality of reinforcement fiberscomposed of elastomeric polymer, and absent of material selected fromthe group consisting of ground rubber tire, tire aggregate and tireparticulate; and introducing and distributing the reinforcement fibersinto the aggregate in the asphalt to produce the fiber-reinforcedasphalt, wherein the elastomeric polymer is selected from the groupconsisting of natural polyisoprene and synthetic polyisoprene.
 16. Afiber-reinforced asphalt, comprising: asphalt cement; a plurality ofreinforcement fibers composed of elastomeric polymer, and absent ofmaterial selected from the group consisting of ground rubber tire, tireaggregate and tire particulate; and aggregate, wherein the plurality ofreinforcement fibers promotes healing of cracks formed withinfield-placed fiber-reinforced asphalt, and wherein the elastomericpolymer is selected from the group consisting of polybutadiene,chloroprene rubber, polychloroprene rubber, butyl rubber,styrene-butadiene rubber, nitrile rubber and mixtures thereof.
 17. Afiber-reinforced asphalt, comprising: asphalt cement; a plurality ofreinforcement fibers composed of elastomeric polymer, and absent ofmaterial selected from the group consisting of ground rubber tire, tireaggregate and tire particulate; and aggregate, wherein the plurality ofreinforcement fibers promotes healing of cracks formed withinfield-placed fiber-reinforced asphalt, and wherein the elastomericpolymer is selected from the group consisting of ethylene propylenerubber, ethylene propylene diene rubber, epichlorohydrin rubber,polyacrylic rubber, silicone rubber, fluorosilicon rubber,fluoroelastomers, perfluoroelastomers, polyether block amides,chlorosulfonated polyethylene, ethylene-vinyl acetate and mixturesthereof.
 18. A method of preparing fiber-reinforced asphalt, comprising:providing asphalt; providing aggregate; providing a plurality ofreinforcement fibers composed of elastomeric polymer, and absent ofmaterial selected from the group consisting of ground rubber tire, tireaggregate and tire particulate; and introducing and distributing thereinforcement fibers into the aggregate in the asphalt to produce thefiber-reinforced asphalt, wherein the elastomeric polymer is selectedfrom the group consisting of polybutadiene, chloroprene rubber,polychloroprene rubber, butyl rubber, styrene-butadiene rubber, nitrilerubber and mixtures thereof.
 19. A method of preparing fiber-reinforcedasphalt, comprising: providing asphalt; providing aggregate; providing aplurality of reinforcement fibers composed of elastomeric polymer, andabsent of material selected from the group consisting of ground rubbertire, tire aggregate and tire particulate; and introducing anddistributing the reinforcement fibers into the aggregate in the asphaltto produce the fiber-reinforced asphalt, wherein the elastomeric polymeris selected from the group consisting of ethylene propylene rubber,ethylene propylene diene rubber, epichlorohydrin rubber, polyacrylicrubber, silicone rubber, fluorosilicon rubber, fluoroelastomers,perfluoroelastomers, polyether block amides, chlorosulfonatedpolyethylene, ethylene-vinyl acetate and mixtures thereof.